1. Field of the Invention
The invention relates to a serial communication device and a method of carrying out serial communication both used for confounding a memory in duplex, and more particularly to such a serial communication device and a method of carrying out serial communication both presenting the same reliability as reliability presented by a parallel bus.
2. Description of the Related Art
FIG. 1 is a block diagram of a conventional system for making communication in duplex confounding.
The system is comprised of a first parallel bus controller 10, a second parallel bus controller 12, a first buffer circuit 11a associated with the first parallel bus controller 10 and electrically connected between the first and second parallel bus controllers 10 and 12, a second buffer circuit 11b associated with the second parallel bus controller 12 and electrically connected between the first buffer circuit 11a and the second parallel bus controller 12, a 32-bit address bus 13, a 32-bit data bus 14, and a 5-bit parity 15.
The 32-bit address bus 13, the 32-bit data bus 14 and the 5-bit parity 15 are all electrically connected between the first and second parallel bus controllers 10 and 12 through the first and second buffer circuits 11a and 11b. 
Communication in duplex confounding between the first and second parallel bus controllers 10 and 12 is made through the 32-bit address bus 13 and the 32-bit data bus 14.
Errors in parallel buses, that is, in the 32-bit address bus 13 and the 32-bit data bus 14 are detected through the 5-bit parity 15.
The above-mentioned conventional system illustrated in FIG. 1 is accompanied with a problem that since the system has to include a lot of signal line for the parallel buses, the system unavoidably has a plurality of buffer circuits 11a and 11b, resulting in much defectiveness in fabrication of the system and high cost for fabricating the system.
It would be possible to accomplish reduction in both cost and defectiveness in fabrication of the system, if the parallel buses are replaced with serial buses. However, the use of serial bus causes another problem that bit errors occur during communication, and hence, it is impossible to ensure the same reliability as reliability obtained when parallel buses are used.
Japanese Patent No. 2971006 (Japanese Unexamined Patent Publication No. 8-265393) has suggested a method of carrying out serial communication in a serial communication controller including at least one first buffer for receiving data and at least one second buffer for transmitting data. In the method, the first buffer is used for receiving data and the second buffer is used for transmitting data when data is received and transmitted in full-duplex communication. The first and second buffers are used only for receiving data when data is received in half-duplex communication. The first and second buffers are used only for transmitting data when data is transmitted in half-duplex communication.
However, the above-mentioned problems remain unsolved even in the method suggested in the above-mentioned Publication.